The present invention relates generally to hydraulic mounts for vibration damping and more particularly, to a hybrid hydraulic mount assembly wherein the apparent viscosity of a magnetic field controllable fluid in a chamber is changed to vary the ability of the mount to control movement. The controllable fluid is provided in a chamber isolated from a hydraulic fluid chamber in the mount.
It is desirable to provide modern vehicles with improved operating smoothness with respect to damping and/or isolating the engine vibrations of the vehicle. In this respect, a variety of mount assemblies are presently available to isolate vehicle vibrations, such as for automobile and truck engines and transmissions. Currently, a great many vehicles incorporate mount assemblies that combine the advantageous properties of elastomeric materials with hydraulic fluids. A hydraulic mount assembly of this type typically includes a reinforced, hollow rubber body that is closed by a resilient diaphragm so as to form a cavity. This cavity separated into two chambers by a plate. The chambers are in fluid communication through a relatively large central orifice in the plate. The first or primary chamber is formed between the partition plate and the body. The secondary chamber is formed between the plate and the diaphragm.
The conventional hydraulic mount assembly can contain a decoupler positioned in the central orifice of the plate that reciprocates in response to vibrations. The decoupler movements alone accommodate small volume changes in the two chambers. At certain small vibratory amplitudes and high frequencies, fluid flow between the chambers is substantially avoided and hydraulic damping does not occur. In this manner, the decoupler functions as a passive tuning device.
In addition to the large central orifice, an outer track with a smaller flow passage is provided. The track in combination with the decoupler provides another passive tuning component. This assembly, in respect to small amplitude vibrating inputs, produces little or no damping. On the other hand, large amplitude inputs produce high-volume, high velocity fluid flow through the track, producing a high level of damping force and smoothing action. The operational characteristics of the hydraulic mount are entirely dependent upon the design of the orifice and track in addition to the characteristics of the damping fluid and elastomeric portions of the mount. As such, while varying amounts of damping are achieved with this design, changing the characteristics of the mount is not possible.
More recently, developments in hydraulic mount technology have led to the addition of electronic control of the mount. This type of mount represents an improvement over previous mounts in that it is responsive to sensed vehicle operating conditions. In this example, the mount provides an additional active tuning aspect. The tuning is accomplished by the use of a variable gate or valve for changing the size of the opening to the track between the two chambers thus controlling the flow of damping fluid therethrough.
An alternate approach to active tuning includes the use of an electro-rheological fluid (ER) or a magnetorheological (MR) fluid disposed in the first and second chambers. In this approach, a number of conductive plates form the partition between the chambers. The plates are provided with an electrical potential thus controlling the flow of fluid between the chambers. The plates of the partition include a number of small flow apertures. In this case some modulation of damping is possible.
It would be desirable to provide a hydraulic mount with continuously variable damping characteristics and active control with a reduced amount of a MR fluid.
One aspect of the present invention provides a hydraulic mount assembly including a body with a main chamber formed therein. A magnetorheological fluid retaining member is positioned in the main chamber forming a magnetorheological chamber adjacent the main chamber. An electrical coil is positioned adjacent the magnetorheological chamber and a plate member is operably connected to the magnetorheological fluid retaining member.
Other aspects of the present invention provide a plate member including a rim portion extending into the magnetorheological chamber. The rim portion can include a metallic portion. The rim portion can be spaced apart from the coil by a predetermined distance and cooperates with the coil to control a magnetic field generated by the coil when the coil is energized.
The plate member can be positioned to separate the main chamber into upper and lower sub-chambers. The plate member can include an inertia track passageway formed therethrough to allow fluid communication between the upper and lower sub-chambers. The plate member can include a valve to control fluid communication between the upper and lower sub-chambers. The valve can be one of a passive valve and an actively controlled valve.
The magnetorheological fluid retaining member can include an upper and lower skirt, each attached respectively to upper and lower surfaces of the plate member at one end, the upper skirt attached to the body at the other end. A ring member can be positioned along the body of the mount. The ring member can include a groove formed in an inner surface thereof, the groove adapted to house the coil therein and position the coil adjacent the rim of the plate member. The upper and lower skirts respectively attach to upper and lower surfaces of the ring member. The magnetorheological chamber can be formed between the upper and lower skirts and the ring member.
The plate member can include a passageway formed therethrough in communication with the upper and lower sub-chambers, the passageway having a greater length than width. The passageway can follow a tortuous path. The passageway can be made tunable to force fluid therethrough at a predetermined resonance.
The plate member can include a control valve, the control valve having an orifice in communication with the upper and lower sub-chambers. The control valve can be one of a passive valve and an active valve. The orifice of the control valve can be provided controllable to allow variable flow of mount fluid therethrough.
Another aspect of the present invention provides a hydraulic mount assembly including housing means for retaining mount fluid, means for retaining magnetorheological fluid, plate means for separating mount fluid with the housing means and means for controlling the movement of the plate.
Yet another aspect of the present invention provides a method of controlling the movement of a hydraulic mount including energizing and de-energizing a coil operably communicating with a magnetorheological fluid within an isolated chamber of the mount in response to a sensed signal and controlling movement of a plate member operably connected to the isolated chamber. In this manner the resistance of the mount to movement of an associated engine or transmission can be made controllable thereby.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.